A vanadium compound is applied as a coating material to improve the electrochemical performance of the lithium-rich layered oxide Li 1.2 Mn 0.6 Ni 0.2 O 2 . The physicochemical properties of the material before and after coating are characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (FT-IR). Results reveal that Li d V 2 O 5 (d is very small) is successfully coated on the as-prepared material, and the crystal properties of the powder have been modified after coating. The formation of the Li d V 2 O 5 coating layer is a result of some Li-ions diffusing from the Li 1.2 Mn 0.6 Ni 0.2 O 2 particle to the coating layer at the interface. The material before and after coating serve as the cathode for lithium-ion batteries and were investigated by galvanostatic measurements within a voltage range of 2.0-4.8 V (vs. Li/Li + ). The initial coulombic efficiency (CE1) of Li 1.2 Mn 0.6 Ni 0.2 O 2 is improved from 71.8% to 87.7% due to the Li d V 2 O 5 coating layer, which can act as an insertion host to accept the lithium ions that could not be inserted back into the bulk lattice during the first discharge process. Additionally, the electrochemical performances (cycling performance and rate capability) of the modified Li 1.2 Mn 0.6 Ni 0.2 O 2 are very superior to the pristine one. The significantly improved electrochemical performances are attributed primarily to: (i) the modified crystal properties after coating; (ii) the amelioration of the charge-transfer resistance after coating; (iii) the coating layer which can contribute to stabilizing the electrode surface by suppressing the side reactions between electrode and electrolyte.
The composite Li1.231Mn0.615Ni0.154O2 has been prepared by a facile combustion synthesis. X‐ray diffraction, thermogravimetric analysis, chemical analysis, X‐ray photoelectron spectroscopy and scanning electron microscope were used to characterize the resultant composite and its precursor. The results show that a well‐crystallized layered hexagonal structured composite Li1.231MnIV0.615NiII0.154O2 is obtained. The resultant composite serves as a cathode material for lithium ion batteries, and galvanostatic charge/discharge tests and cyclic voltammetry revealed that the composite exhibits excellent electrochemical performance. The as‐prepared electrode delivers an average specific energy density as high as 795 W h kg–1 in the range 4.8–2.0 V (vs. Li/Li+) at a constant current density of 20 mA g–1.
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